Originally Posted by
rick130
Firstly, Detroit Lockers and Tru Tracs used to be made by a company called Tractech, now been swallowed up by Eaton in the US.
Secondly, a Detroit Locker is a pair of dog clutches splined to smaller hubs which are splined to the axles, with a central dog ring connected to the diff case. This locks the two outer dog faces together, not sprags. On differential wheel speed an outer dog ring can be forced against spring pressure to unlock, giving differential action. As soon as both wheels are rotating at equal speeds, the springs force the dogs to re-engage, locking the diff.
A sprag clutch is a different animal altogether, and will unlock on the over-run, and I'm assuming in reverse.
A famous locking race diff from the seventies was the Wiseman (sp?) Locker that was basically a sprag clutch and cone. It locked 100% but unlocked on the over-run, which is important in a race car as it doesn't then cause corner entry understeer. A Detroit Locker remains locked as you describe, causing corner entry understeer (as does a spool) and only unlocks under differential wheel speed.
A Detroit Locker or No Spin locks the same forward or reverse.